Koramik
There are a few threads about it here. I have the same issue and tried all of the suggested fixes but still the problem occurs now and then. I have not been able to pinpoint any exact setting or situation where the problem can be replicated reliably. It occurs regardless of network (4G/5G only etc), new SIM card, e-SIM etc. I have a P8Pro fully updated. I think the problem is less the last month but still occurs. When the problem occurs I only get a "missed-call-SMS" from my carrier, no call what so ever.